1. Field of the Invention
This invention relates to a novel ABS resin composition improved in fire retardance and workability. More particularly, this invention relates to a resinous composition comprising a blend mixture of an ABS resin and either a copolymer resin consisting essentially of vinyl chloride and a higher alkyl vinyl ether or a vinyl chloride resin compound containing the copolymer.
2. Description of the Prior Art
ABS resins (acrylonitrile-butadiene-styrene resins) are of easy-combustibility, and a fire-retarded ABS resin has been keenly needed.
ABS resins have been generally incorporated with fire retardant additives such as halogen-containing compounds and phosphorus-containing compounds and, if desired, together with fire retardant auxiliaries such as antimony trioxide.
Especially, vinyl chloride resins (hereinafter referred to as PVC) have been widely employed as a fire retardant for ABS resins, since PVC is readily blended with ABS resins and does not cause decrease in mechanical strength, and bleeding and weathering after a long time of use unlike the case where low-molecular retardant additives such as halogen compounds are employed.
As noted above PVC is an excellent fire retardant for ABS resin, but there remain some processing problems owing to the difference in heat stabilities between PVC and ABS resin. This is, PVC is inferior in heat stability to ABS resin. When a blend of PVC and ABS resin is molded at a temperature suitable for processing ABS resin, PVC undergoes thermal decomposition. On the other hand, when the blend is processed at a lower temperature suitable for PVC, the processing of the blend is extremely difficult because of its very high melt viscosity.
Addition of plasticizers such as dioctyl phthalate and dibutyl phthalate has been proposed so as to eliminate these defects, but this method results in decrease in the heat distortion temperature of the blend as well as deterioration of fire retardance and great decrease in stiffness inherent in ABS resin compositions.